Scientists confirm: Pesticides kill America's honey bees

Honey bees are quickly disappearing from the US – a phenomenon that has left scientists baffled. But new research shows that bees exposed to common agricultural chemicals while pollinating US crops are less likely to resist a parasitic infection.

As a result of chemical exposure, honey bees are more likely to
succumb to the lethal Nosema ceranae parasite and die from
the resulting complications.

Scientists from the University of Maryland and the US Department
of Agriculture on Wednesday published a study that linked chemicals, including
fungicides, to the mass
die-offs. Scientists have long struggled to find the cause
behind the Colony Collapse Disorder (CCD), in which an estimated
10 million beehives at an average value of $200 each have been
lost since 2006.

Last winter, the honey bee population declined by 31.1 percent,
with some beekeepers reporting losses of 90 to 100 percent of
their bee populations. Scientists are concerned that
“Beemageddon” could cause the collapse of the $200 billion
agriculture industry, since more than 100 US crops rely on honey
bees to pollinate them.

The new findings are key in determining one of the causes of the
CCD, but they fail to explain why entire beehives sometimes die
at once.

UMD and DOA researchers found that pollen samples in fields
ranging from Delaware to Maine contained nine different
agricultural chemicals, including fungicides, herbicides,
insecticides and miticides. One particular sample even contained
21 different agricultural chemicals. To test their theory, they
fed pesticide-ridden pollen samples to healthy bees and then
infected them with the parasite. They found that the pesticides
hindered the bees’ abilities to resist the infection, thus
contributing to their deaths. The fungicide chlorothalonil was
particularly damaging, tripling the risks of parasitic
infection.

“We don’t think of fungicides as having a negative effect on
bees, because they’re not designed to kill insects,” Dennis
vanEngelsdorp, the study’s senior author, said in a news release.

He explained that federal regulations restrict the use of
insecticides while pollinators are foraging, but noted that
“there are no such restrictions on fungicides, so you’ll often
see fungicide applications going on while bees are foraging on
the crop. The finding suggests that we have to reconsider that
policy.”

Bees are declining at such a fast rate that one bad winter could
trigger an agricultural disaster. California’s almond crop would
be hit particularly hard, since the state supplies 80 percent of
the world’s almonds. Pollinating California’s 760,000 acres of
almond fields requires 1.5 million out-of-state bee colonies,
which makes up 60 percent of the country’s beehives. The CCD is a
major threat to this $4 billion industry.

Entomologists suspect that a number of other factors also
contribute to the CCD, including climate change, habitat
destructing and handling practices that expose bees to foreign
pathogens. But the effect of agricultural chemicals is
particularly alarming, especially since the US does not have laws
banning the use of the pesticides that are affecting bee health.

“The pesticide issue in itself is much more complex than we
have led to believe,” vanEngelsdorp said. “It’s a lot more
complicated than just one product, which means of course the
solution does not lie in just banning one class of product.”